It is now possible to routinely measure the monochromatic aberrations of the human eye. However, one cannot yet measure the visual acuity that will result from a given set of wavefront aberrations. One reason to seek a prediction of acuity from aberrations is the possibility of automated objective measurement of visual acuity, and of automated prescription of sphero-cylindrical corrections. However, it has been shown that correcting the spherical and cylindrical components of the aberrations (equivalent to minimizing the RMS error of the wavefront) does not provide best acuity. Thus these automated procedures must await a more sophisticated metric that can predict acuity from an arbitrary set of aberrations.
In the last decade there has been a revolution in measurement and treatment of visual optical defects. This revolution has included the development of aberrometers simple enough to be used in the clinic, refinement of methods of laser surgery for optical correction, and development of various optical implants, notably intra-ocular lenses (IOL). In all of these, measurement and interpretation of wavefront aberrations (WFAs) has played an important role. They are a simple and comprehensive way of describing the state of the optical system. In spite of this, there is at present no accepted, reliable way of converting WFAs to visual acuity, which is a standard measure of quality of vision. The WFA Metric allows calculation of visual acuity from wavefront aberrations.
What is needed is an approach, including one or more metrics, that allows a prediction of visual acuity, for a human or other animal, based on estimated wavefront aberrations (WFAs) measured or otherwise determined for the test subject. Preferably, the approach should allow acuity predictions for different optotypes, such as Sloan letters, Snellen e's, Landolt C's, Lea symbols, Chinese or Japanese characters and others. Preferably, the approach should permit incorporation of different, possibly subject-specific, neural transfer functions.